Signaling system



Dec. 25, 1928.

L. F. BIRD SIGNALING SYSTEM Filed Oct. 21, 1927 LMMLT H M WM 44$ H ney Inventor Lester F Bird is Attor Patented Dec. 25, 1928.

PATENT QFFIQE- LESTER E. BIRD, OF IRVINGTON, NEW JERSEY, ASSIGNOR T GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

SIGNALING SYSTEM.

Application filed October 21, 1927. Serial No. 227,821.

My invention relates to signaling systems employing oscillation generators and more particularly to signaling systems adapted for duplex operation.

Heretofore in certain systems of the type indicated means have been provided whereby the production of oscillations of the oscilla tion generator may be controlled by the signaling currents. Thus when the operator speaks into the microphone the production of oscillations by the oscillator will be initiated and continued so long as the signal currents continue. When the signal currents cease the oscillator becomes inoperative and the system will be in readiness for reception of signals from a remote point upon a carrier wave of either the same or other frequencies. Systems adapted for the accomplishment of this purpose have been proposedby Mr. Emmett F. Carter in his applications, Serial No. 752,243, filed November 25, 1924-, and Serial No. 5,148, filed January 27, 1925.

The purpose of my present invention is to provide means for controlling the production of oscillations in response to signal currents in which modulation through the control device, during the firstsyllable of each word, will be substantially eliminated. In the systems commonly used previously smoothing means, such as condensers, have been employedin the anode circuit of the control device upon the grid of which the signal currents are directly impressed. It has been found that. during the time when no signal current is impressed upon the grid of the con trol device the sn'ioothing condenser will as sums a. certain charge. This charge will dissipate itself through the control device upon the initiation of control currents upon the grid thereof. During the period of this dissipation and while the condenser is assuming a normal operating potential it serves inefiiciently to smooth the voice or signal wave and as a result some modulation of the carrier wave will take place through the control device. This modulation will have the effect of producing at the receiver a distorted and unpleasant sounding first syllable of each word.

In other systems instead of impressing the voice wave directly upon the grid of the control. tube it has been impressed upon the grid of an additional tube which serves to rectify an alternating current of normal frequency and to supply the rectified potential to the grid of the control device. In this system if the voice wave is initiated at a time in the alternating current cycle when the anode of the rectifying device has just become negative with respect to the cathode thereof, it will be seen that the control tube will not re spond until a period equal to a half cycle of the alternating current wave has elapsed.

In accordance with my invention means are provided whereby the voice or signaling current itself may be rectified and thereby used to control the potential of the grid of the control device. By this means it will be seen that the time elapsed between the initiation of the signal currents and that of the carrier oscillations Will be reduced, and furthermore, that the condensers which are used for smoothing may be considerably reduced in size, In addition to these features my system has the advantage that the above-morn tioned modulation during the first syllable will be substantially reduced.

The novel features which I believe to be characteristic of my invention will be set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation will best be understood by reference to the following description taken in connection with the accompanying drawing in which the single figure illustrates one embodiment of my invention.

Referring to the drawing, 1 represents an oscillation generator of the three clement electron discharge type which is provided with the usual oscillatory circuit 2. This generator is adapted to supply high frequency currents through the coupling condenser 3 to the grid of a high frequency amplifier at from which they are supplied through the output transformer 5 and coupling condensers 6 to a radiating system or wire lino conductors 7. The anode circuit of the electron discharge device 1 extends through a radio frequency choke coil 8. source of potential 9, space between the oath ode and anode of the control device 10, conductor 11 and space between the cathode and anode of the oscillation generator 1. It will thus be seen that the oscillation generator will be inoperative except at times when the grid of the control device is at such a potential that current may flow in the anode circuit of the oscillation generator. The anode circuit of the amplifier 4.- extends through the primary winding of the trans former 5, niodudation reactor 18, source of potential l l, conductor 15 and space between the cathode and anode of the electron discharge device 4t. 16 represents the operators station from which signal currents may be supplied through the hybrid coil 17 and transformer 18 from which they may be impressed upon the grid of an electron discharge device 19 by means of which they are caused to modulate the high 'irequenc currents produced by the oscillator 1 in a manner well-known in the art. These currents are likewise impressed upon the grid of an electron discharge device 20 which is here employed as an amplifier. From this device the signal currents are supplied through the transformer 21 to a rectifying device 23 represents a source of potential which is connected in circuit with a resistance 2st and the grid 01"" the control device 10. This potential is such that when no signal currents are impressed upon the rectifying device 22 the grid of the device 10 will be biased negatively to such an extent that the anode cathode impedance of this device will be so high that the oscillation generator will be rendered inoperative. When signal current is impressed through the transformer 21 upon the rectifier 22 it causes a direct current potential to appear across the resistance 24:. This potential will be of opposite polarity from that of the source 2-3 and will be suf icient to cause the g 'd o1 the device 10 to be varied in a positire direction su'fiiciently to permit the flow ot anode current in this device, and thereby to cause the production of oscillations by the oscillation generator 1. 25 represents a condenser which is connected in parallel with the resistance 2% for the purpose of smoothing out the signal wave, and thereby causing a' substantially smooth potential to appear upon the grid of the device 10. The condenser 25 will be of such capacity that it will become fully charged during the first tour or five cycles of the voice wave and will discharge through the resistance at the end of each word. Similarly 526 represents a condenser which is connected between the cathode and anode of the control device in the usual manner for smoothing purposes.

The cathodes of each oi: the electron discharge devices are represented. as energized by means of? alternating currents through suitable cathode transformers only the secondary windings 27 of which are shown. The receiving apparatus which is commonly associated with systems of this nature is represented at 28 and is connected between suitable terminals of the hybrid coils 5 and 17.

By means of a system such as T have described it will be seen that a substantially smooth potentialis impressed upon the grid 10 and consequently no appreciable modulation can take place through this device. Thecondensers 25 and 26 may be made substantially smaller than those of the prior systems with the result that the time elapsing between the initiation of voice currents and the ii'iit-iation of the carrier wave is reduced. In other words the time required for these condensers to assume a normally operating potential is reduced. 7

lVhile I have shown and described a sinembodin'ient of my invention it will, of course, be understood that I do not wish to be limited thereto, since modifications both in the circuit arangement and in the instrun'ientalities employed may be made without departing from the spirit and scope of my invention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a signaling system, an electron di.s charge oscillator, an electron discharge device connected in the anode-cathode circuit of said oscillator and having impedance sufficiently high normally to prevent the production of oscillations by said oscillator, a source of signal current, means for rectifying said signal current and means for supplying a potential resulting from rectification of said signaling currents to said discharge device to reduce the in'ipedance thereof and thereby to control the operation of said oscillator.

2. In a signaling system, an electron discharge osoillator, a second electron discharge device connected in the anode-cathode circuit of said oscillator and having impedance suiiiciently high norn'ially to preclude the production of oscillations by said oscillator, a source of signal current, means for rectifying said signal current and means for supplying a substantially smooth potential resultingfrom rectification of said signal currents to said second discharge device to reduce the impedance thereof and thereby to cause said oscillator to produce oscillations.

3. In a signaling system, an electron discharge oscillator, a second electron discharge device havin an anode, a cathode and a control element, said anode and cathode bcii'ig connected in the anode circuit of said oscillator. means for impressing a negative potential upon said control element su'tlicient to subs antially preclude the production ot oscillations by said oscillator, a source of signal current, means for rectifying said signal current, means for smoothing the potential resulting from rectification of said signal current and for varying the potential on said control element in accordance therewith thereby to cause said oscillator to produce oscillations. V

a. In a signaling system, an electron discharge oscillator, a second electron discharge device having a control element said dellU lit)

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in'ipressing a substantially smooth potential 10 upon said control element in opposition to said negative potential, the sum of said potentials being suflicient to cause the production of oscillations by said oscillator.

In Witness whereof, I have hereunto set 15 my hand this 13th day of October, 1927.

LESTER F. BIRD,

GERTIFECATE 0F CORREGTIGN Patent No. 1,696,590. Granted Deeember 25, 1928, to

LESTER F. BIRD.

it is hereby certified that error appears in the printed specification of the above numbered patent requiring eorreetioti as follows: Page 3, line 4, claim 4, after the Word "on" insert the word "said"; and that the said Letters Patent shouid be read With this correction therein that the same may conform to the record of the ease in the Patent Office.

Signed and sealed thisSth day of February, A. D. 1929.

M. J. Moore, (Seal) Acting Commissioner of Patents. 

